Clutch with torque measuring device

ABSTRACT

In fluid pressure or electromagnetically operated clutches, the transmitted torque is measured by strain gauges incorporated in rotating clutch members. The strain gauges are energized and the signal from them conveyed to stationary control equipment by way of co-operating rotating and fixed coils of which one, in the case of the electromagnetically actuated clutch, can be energized to operate the clutch.

DESCRIPTION

The invention relates to the measurement of torque transmitted by arotating member.

The application is concerned with the measurement of torque transmittedby a clutch element in a clutch of the kind comprising a drive memberfor receiving a rotational drive, and a clutch element which is axiallymovable between a first position in which the rotational drive isapplied by way of the clutch element to a driven member and a secondposition in which the drive is not so applied. Such clutches are widelyused in industrial machinery and it would be advantageous in manyapplications to be able to measure the torque being transmitted throughthe clutch during operation, as for monitoring the performance of themachines in which they are incorporated and for control purposes, forexample, to prevent overloading.

In accordance with the invention, a clutch of the kind described aboveis characterised by transducer means responsive to the torquetransmitted in the clutch in the first position of the clutch element toprovide an output signal to first electrical coupling means, the firstelectrical coupling means co-operating with second electrical couplingmeans carried by a stationary portion of the clutch to convey the outputsignal to a stationary electrical treatment means.

By the use of the coupling means operating between the torquetransmitting member and a stationary member, the former need carry onlythe transducer or sensor means and the first coupling member. Thecoupling means can operate inductively, and can comprise a first andsecond electromagnetic coil located on respective adjacent surfaces ofthe transmitting member and the stationary member. The coupling meanscan convey any power needed to energise the transducer or sensor meansfrom the stationary units, as well as conveying the torque dependentoutput to it. The stationary unit can be located remotely from thetorque transmitting member so as to be shielded from vibration and oilsplash for example when the member is incorporated in a brake or clutchmechanism. The stationary unit can employ the torque dependent outputfor recording and/or display and/or control purposes. The outputsupplied to the stationary unit can be the raw transducer output, butthis can be processed by miniaturised processing means carried by thetorque transmitting member.

Thus, in a clutch comprising a rotatable driving member, a rotatablemember to be driven, and a clutch element selectively movable elementbetween operative and inoperative positions in which it respectivelytransmits and does not transmit a drive from the driving member to thedriven member, there can be provided in accordance with the invention, atransducer means in the form of strain gauge means incorporated in theclutch element, so as to respond to the torque transmitted thereby, anda transformer coupled tuned oscillator, for transmitting power toenergizing the strain gauge means and for transmitting the strain gaugemeans output from the clutch. The primary and secondary windings of thecoupling transformer are preferably located on respective opposed facesof the clutch element and of a stationary clutch portion having aspacing between them which remains at least approximately constantduring operation.

The strain gauge or other sensor means output can be employed formeasurement purposes, for example, to provide a measure of actual torquetransmission either continuous or when required. The output can berecorded if desired, and can instead or in addition be applied to amicroprocessor capable of treating the output so as to provide a desiredfunction. Thus, in a clutch, the microprocessor could be arranged tostore a normal operating torque level, either selectively input orgenerated from past clutch experience, and to give an indication of anydeparture therefrom exceeding the predetermined level, and/or toactivate an alarm and/or to disengage the clutch to prevent overloaddamage. The invention can thus be embodied to function as a torquelimiter, and, in a brake mechanism, to apply torque betweenpredetermined maximum and minimum levels.

In a friction clutch, the processor could operate to cushion shock loadsby momentary disengagement followed by re-engagement, so that machineacceleration could be controlled.

In a fluid-pressure operated clutch, the operating pressure could becontrolled in response to the torque sensor output to a levelappropriate to the actual torque being transmitted. The working life ofthe bearings of the clutch could thus be extended because maximumpressures would be applied only when needed. The controller ormicroprocessor could include suitable memory for recording the hours ofoperation of the clutch, if desired, to assist servicing.

The invention is further described below, by way of example, withreference to the accompanying drawings, in which:

FIG. 1 is a schematic sectional side view of a fluid pressure operatedtoothed clutch embodying the present invention;

FIG. 2 is a fragmentary axial view on a larger scale of a part of theclutch of FIG. 1;

FIG. 3 is a block diagram illustrating electrical control arrangementsfor the clutch of FIG. 1; and

FIG. 4 is a view similar to that of FIG. 1 of an electromagneticallyoperated toothed clutch embodying the invention.

The clutch illustrated in FIGS. 1 and 2 comprises a fixed housing orsupport of which only a support member 2 of annular form is shown in thedrawings. A drive shaft 4 coaxially journalled within .the supportmember 2 by a bearing 5 can be rotatably driven by a motor (not shown).

The support member 2 is externally stepped at what will be referred toas the forward end and a drive ring 6 is received externally around thereduced diameter portion forward of the step. The drive ring 6 containswithin a peripheral groove a seal element 7 engaging with the reduceddiameter portion of the support member 2. The drive ring 6 also has asleeve portion projecting rearwardly over the larger diameter portion ofthe support member 2 for sealing engagement with a seal element 9receivedwithin a peripheral groove of the support member.

The end face of the drive ring 6 adjacent the support member step isrecessed and a passage 10 extends from the exterior surface of thesupportmember to the chamber formed by the recess and the step. Thepassage 10 communicates by way of tubing 11 with a fluid pressure source12 from which a pressure fluid, for example, air or an hydraulic fluid,can be supplied through the tubing and the passage to the chamber, tocause the drive ring 6 to move on the support member 2 away from thestep.

The drive shaft 4 has longitudinally extending splines 14 and an annularclutch element 20 surrounding the shaft has grooves formed in its innersurface receiving the splines, so that the clutch element is rotatablydriven by the shaft and is capable of movement axially along it. Theclutch element 20 has around the grooves an inner portion 21 received inthe annular space between the support ring 2 and the drive shaft 4 andan intermediate portion 22 extending radially outwardly from the forwardend of the inner portion.

The clutch element 20 also has an outer portion radially adjacent thedrivering 6 and having an annular array of forwardly extending radiallydirectedclutch teeth 24. A driven clutch member 25 has an annular arrayof radiallydirected teeth 26 for co-operation with the teeth 24.

A further bearing 29 is provided between the outer portion of the clutchelement 20, opposite the teeth 24, and the non-rotating drive ring 6 toaccommodate the relative rotation of these parts and transmit the fluidpressure generated thrust of the drive ring to the clutch element.

In the position shown in FIG. 1, the teeth 24, 26 are spaced slightlyapart, so the clutch is disengaged, with the clutch element 20 rotatingfreely with the drive shaft 4. Engagement is affected by application offluid pressure through the passage 10 to causes the drive ring 6 to moveaxially to the left as shown, and to push the clutch element 20 in thesame direction by forces transmitted through the bearing 29, until thetwosets of teeth are engaged together. Torque is then supplied from thedrive shaft 4 through the clutch element 20 to the driven member 25. Aspring 30acting between the shaft 4 and the clutch element 20 is loadedby this movement of the clutch element.

When the clutch is to be disengaged, the fluid pressure is released, andthe spring 30 effects positive return of the clutch element 20 to theposition shown in which the teeth 24, 26 are spaced from engagement.

The torque transmitted from the drive shaft 4 to the driven member 25 ismeasured in accordance with the invention by sensor means located in theclutch element and constituted by a strain gauge bridge which can be atemperature compensating bridge if required. The strain gauges 32 of thebridge are accommodated within kidney-shaped slots 33 formed in theintermediate portion 22 of the clutch element 20.

Electrical communication between the strain gauge sensor means, which ofcourse rotates in use, and stationary equipment carried by the fixedhousing or support, or remotely located, is effectedelectro-magnetically by co-operating coil means 35,36 set into opposedrecesses at the outer surface of the clutch element inner portion 21 andat the inner surface ofthe reduced diameter portion of the supportmember 2. The stationary coil primary means 36 on the support member 2has a greater axial length than the secondary coil means 35 on theclutch element 20 so that the coils areinductively coupled whatever theaxial position of the clutch element 20. Leads 37 extend between thestrain gauges 32 and the coil means 35, and leads 39 extend from thecoil means 36 to the stationary treatment or receiver equipment. Thisequipment can comprise means for displaying and/or recording anindication of the torque being transmitted and/or means for exercising adesired control function.

The equipment can conveniently comprise a control unit such as the unit45 illustrated schematically in FIG. 3.

The control unit 45 comprises a power supply unit 46 receiving a mainspower supply on a line 47 and control logic 49 responsive to an on/offcontrol 50, which may be remotely located. The power supply unit 46 alsoenergizes the strain gauge bridge by way of the leads 39 and coils35,36. As these components carry the strain gauge output also, the leads39 connect to a modulator/de-modulator unit 51 incorporated in thecontrol unit, through which the strain gauge bridge is energized andfrom which the strain gauge output is supplied to the control logic 49.

A solenoid valve 52 operative in the supply line 11 between the fluidpressure source 12 and the passage 10 is responsive to an output fromthe control logic and may be incorporated in the control unit 45. Thecontrol logic 49 is arranged to exercise a suitable control function,for example,as described above, as it may respond to the strain gaugeoutput so as to cause the solenoid valve 52 to cut off the fluidpressure supply to the clutch if the torque transmitted by the clutchelement 20 exceeds a predetermined value or range of values, which maybe preset into a memory of the control logic, or may be established bythe control logic in consequence of previous clutch experience.

The control unit 45 also includes a communications interface 54 allowingthe value within the logic 49 of the torque being supplied through theclutch to be displayed and/or recorded externally and/or remotely of theunit 45. The clutch performance can thus be monitored. The interface 54also allows access to the control logic to permit selective adjustmentof the control function, for example, of the predetermined level. Thesensitivity of the clutch can thus be altered, remotely if required, andduring operation, as when there is a greater risk of overloading.

The clutch illustrated in FIG. 4 again comprises a fixed housing orsupportincluding an annular support member 60 with a drive member 61coaxially journalled within it, by bearings 62. The support member 60has an annularrecess open to the left as shown in which is received astationary coil 64.The drive member 61 has an external flange 65 axiallyadjacent the coil 64 and which functions as a clutch element, beingprovided with clutch teeth 66 extending axially away from the coil 64 atits outer edge.

A driven member 70 is journalled on the drive member 61 by bearings 71and carries a movable annular clutch element 72 at a transverse faceopposite the flange 65. The clutch element 72 is carried by the member70 on axially projecting bolts 74 for axial movement towards and awayfrom the flange 65. The bolts 74 extend from the driven member 70 intorecesses in the element 72 opening from the face opposite the flange 65.Compression springs 75 received on the bolts 74 between their heads andthe floors of the recesses act to urge the element 72 against the drivenmember 70. A ring of clutch teeth 76 is provided at the outer peripheryof the element 72 for engagement with the teeth 66.

In the position shown in FIG. 4, the teeth 66,76 are spaced slightlyapart,so the clutch is disengaged, with the driven member 70 free on thedrive member 61. Engagement is effected by energization of the coil 64so as to move the clutch element 72 to the right as shown, compressingthe springs 75, until the two sets of teeth are engaged together. Torqueis then supplied from the drive member 61 through the clutch element 72to the driven member 70.

When the clutch is to be disengaged, the coil 64 is de-energized and thesprings 75 effect positive return of the clutch element 72 to thepositionshown in which the teeth 66,76 are spaced apart.

The torque transmitted is measured by sensor means, located in theflange 65, which can again be constituted by a strain gauge bridge,temperature compensated if required. The strain gauges 77 of the bridgecan be accommodated in the flange in the same way as the gauges 32 areaccommodated in the clutch element 20.

Electrical communication between the rotating strain gauge sensor meansandstationary equipment is effected electro-magnetically by way of acoil 79 set into a recess in the flange 65 so as to co-operate with thecoil 64. The coil 64 thus functions similarly to the fixed coil 36 ofFIG. 1 but inaddition serves to effect engagement of the clutch. Thestationary equipment to which the coil 64 is connected can comprisemeans for displaying and/or recording an indication of the torque beingtransmitted and/or means for receiving or exercising a desired controlfunction. The equipment can thus correspond to the unit 45 modified toexercise control of the clutch position by energization orde-energization of the coil 64 instead of by operation of the solenoidvalve 52.

The invention can be embodied in a variety of ways other than asspecifically described and illustrated.

I claim:
 1. A clutch device comprising:a frame, a drive member forreceiving a rotational drive, a drivable member, a clutch element,electromagnetic coil means for moving said clutch element between afirst position in which said rotational drive is applied by way of saidclutch element to said drivable member and a second position in whichsaid drive is not so applied, transducer means responsive to the torquetransmitted in said clutch in said first position of said clutch elementto provide an output signal, electrical treatment means for treatingsaid output signal, first electrical coupling means receiving saidoutput signal, and second electrical coupling means carried by saidclutch frame, said first electrical coupling means co-operating withsecond electrical coupling means to convey said output signal to saidelectrical treatment means and said electromagnetic coil means formoving said clutch functioning also as said second electrical couplingmeans.
 2. The device of claim 1 wherein said transducer means is locatedon said clutch element and wherein the first and second electricalcoupling means are located respectively on said clutch element and onsaid frame in concentric relationship.
 3. The device of claim 1 whereinsaid transducer means is located on said drive member and wherein saidfirst and second electrical coupling means are located respectively onsaid drive member and said frame in axially opposed relationship.
 4. Thedevice of claim 1 wherein said first and second electrical couplingmeans comprises inductively coupled electromagnetic coils.
 5. The deviceof claim 1 wherein said transducer means requires to be electricallyenergized, and wherein electrical energization of said transducer meansis effected by way of said first and second electrical coupling means.6. The device of claim 1 wherein said transducer means comprises atleast one strain gauge.
 7. The device of claim 1 wherein said electricaltreatment means is adapted to display and/or record said transmittedtorque as measured by said transducer means.
 8. The device of claim 1wherein said electrical treatment means is adapted to sense departure ofsaid transmitted torque as measured by the transducer means from atleast one of a predetermined value and a predetermined range of values,and to indicate such a departure and/or to exercise a control functionin response to the sensing of such a departure.
 9. The device of claim 8further comprising means for selective adjustment of said predeterminedvalue and/or the predetermined range.
 10. The device of claim 8 whereinsaid electrical treatment means includes means whereby saidpredetermined value and/or the predetermined range are adjusted inresponse to clutch experience.
 11. The device of claim 8 wherein saidcontrol function comprises disengagement of said clutch eithermomentarily or until reset.
 12. A clutch device comprising:a supportframe, a rotary drive member journaled in said support frame, a drivableclutch member journaled in said frame, a clutch element carried by saidrotary drive member for rotation therewith and for movement along theaxis of said rotation between a first position in which said clutchelement couples said rotary drive member to said drivable clutch memberand a second position in which said rotary drive member is decoupledfrom said drivable clutch member, clutch control means selectivelyoperable to move said clutch element between said first and secondpositions thereof, transducer means mounted on said clutch element, saidtransducer means being adapted to provide an output signal dependent ontorque transmitted by said clutch element in said first positionthereof, electrical treatment means carried by said frame, andelectrical transmission means transmitting said output signal to saidelectrical treatment means, said electrical transmission comprisingco-operating first and second non-contacting members carriedrespectively by said clutch element and said frame.
 13. The clutchdevice of claim 12 wherein said clutch element comprises an innerportion adapted to engage said rotary drive shaft, an outer portion atwhich said clutch element is adapted to engage said drivable clutchmember in said first position of said clutch element, and anintermediate portion between said inner and outer portions, saidtransducer means being mounted on said clutch element at saidintermediate portion thereof.
 14. The device of claim 12 wherein saidclutch control means comprises fluid-pressure-operated means.
 15. Thedevice of claim 12 wherein said first and second non-contacting memberscomprise first and second electromagnetic coils and wherein said secondelectromagnetic coil is additionally comprised within said clutchcontrol means.
 16. The device of claim 12 wherein said electricaltreatment means is adapted to sense departure of said transmitted torqueas measured by said output signal from one of a predetermined value anda predetermined range of values, and to indicate said sensed departure.17. The device of claim 16 wherein said electrical treatment means isadapted to exercise a control function in response to the sensing ofsaid departure, said control function comprising movement of said clutchelement to said second position thereof.
 18. A clutch devicecomprising:a support frame, a drive member journaled in said supportframe for rotation about an axis, a drivable member rotatable about saidaxis, a clutch member rotatable about said axis, said clutch member andone of said drive member and said drivable member having co-operatinginterengageable annular clutch formations centered on said axis, saidclutch member being attached to the other one of said drive member andsaid drivable member, said clutch member being movable along said axisbetween a first position in which said clutch formations areinterengaged whereby said clutch member couples said drive member tosaid drivable member and a second position in which said clutchformations are disengaged whereby said drive member is decoupled fromsaid drivable member, control means selectively operable to move saidclutch member between said first and second positions thereof,transducer means mounted on one of said clutch member and the one ofsaid drive member and said drivable member having said clutch formation,said transducer means being located at a position radially between saidaxis and said clutch formations, and said transducer means being adaptedto provide an output signal dependent on torque transmitted through saidclutch device in said first position of said clutch member, electricaltreatment means responsive to said output signal, and electricaltransmission means transmitting said output signal to said electricaltreatment means, said electrical transmission comprising co-operatingfirst and second non-contacting members carried respectively by saidsupport frame and by said one of said clutch member and said drivemember and said drivable member having said transducer means mountedthereon.
 19. The device of claim 18 wherein said clutch member ismounted on said drivable member, said drivable member having said clutchformation.
 20. The device of claim 19 wherein said drivable member isjournaled on said drive member.
 21. The device of claim 18 wherein saidclutch member is mounted on said drive member, said drivable memberhaving said clutch formation.
 22. The device of claim 18 wherein saidcontrol means comprises an electromagnetic coil mounted on said frameand means for selectively energizing said coil, and wherein saidelectromagnetic coil is adapted to function also as said secondnon-contacting member.
 23. The device of claim 18 wherein saidtransducer means comprises at least one strain gauge.
 24. The device ofclaim 18 wherein said electrical treatment means is adapted to sensedeparture of said transmitted torque as represented by said outputsignal from at least one of a predetermined value and a predeterminedrange of values.
 25. The device of claim 24 wherein said electricaltreatment means includes means whereby at least one of saidpredetermined value and said predetermined range of values is adjustedin response to clutch experience.